ABSORB II: Similar Clinical Outcomes, Less Angina with Bioresorbable Scaffold vs. EES

In the first randomized trial pitting an everolimus-eluting bioresorbable scaffold against a metallic stent that releases the same drug, researchers found similar safety and efficacy at 1 year in patients with up to two de novo lesions. Results of the ABSORB II trial, presented in a late-breaking trial session at TCT 2014 and simultaneously published in the Lancet, suggest that operators may have not been aggressive enough in dilating the newer device and that practice corrections going forward may improve outcomes.

Patrick W. Serruys, MD, PhD, of Erasmus Medical Center, Rotterdam, the Netherlands, and colleagues randomized 501 patients with evidence of myocardial ischemia and no more than two de novo lesions in a 2:1 fashion to receive everolimus-eluting bioresorbable scaffolds (Absorb, Abbott Vascular; 335 patients and 364 lesions) or metallic stents (Xience, Abbott Vascular; 166 patients and 182 lesions) at 46 sites in Europe and New Zealand. All patients underwent coronary angiography, IVUS and IVUS-virtual histology before and after device implantation. One-quarter had diabetes, and about 20% presented with unstable angina. All but two lesions in the metallic stent group were predilated.

On quantitative IVUS, both preprocedural vessel area (P=.02) and plaque (P=.01) were larger in the metallic stent group compared with the bioresorbable scaffold group, but rates of clinical success were similar.

Dilatation pressure was higher (P=.01) and balloon diameter at the highest pressure during implantation or postdilatation was larger (P=.02) in the metallic stent group. Therefore, the acute gain in minimum lumen diameter and area, as well as the final minimum lumen diameter and area, were larger in the metallic stent group compared with the bioresorbable scaffold group (P<.001 for all).

Cumulative angina rates at 1 year were lower with the bioresorbable scaffold than with the metallic stent (22% vs. 30%; P=.04), yet results from the Seattle Angina Questionnaire showed no difference between the devices. All clinical secondary outcomes also were similar, although there were trends toward more MI and less revascularization with the bioresorbable scaffold (see Figure). Two instances of scaffold thrombosis were observed in the bioresorbable scaffold group, both within 2 days.

According to the Lancet paper, the “reported reduction of angina through adverse event reporting warrants further clinical and physiological investigation.”

Data on the trial’s co-primary endpoints — vasomotion and minimum lumen diameter after nitrate administration minus the post-procedure value — will be reported at 3 years. Serruys commented in a press conference that when ABSORB II commenced, common practice was to be “overcautious” with deploying bioresorbable stents because of concern over the fragility of the polymer. Now, he said, “this is something that we have corrected.”

• Serruys reports serving on the advisory board of Abbott Vascular.